The invention relates to a starting control to control a hydraulic piston/cylinder unit, in particular to control a multi-disc clutch. The present invention further relates to a multi-disc clutch having a disc package which can be compressed by a piston, having a feed for a hydraulic medium being disposed in such a way that a force directed to the disc package can be generated on the piston when pressure is applied to the feed, and having one or more restoring elements which apply a counter-force to the piston working against the force which can be applied by the hydraulic medium. The present invention further relates to a vehicle, in particular a commercial vehicle, having a piston/cylinder unit which can be subjected to a hydraulic medium.
A multi-disc clutch possesses several clutch discs disposed on a drive shaft which clutch disks are, when the clutch is actuated, connected non-positively to gears or disks provided between the discs and being in communication with a drive shaft and allowing in this way the transfer of a torque. When the clutch is actuated, a movably disposed piston is subjected to hydraulic oil and thus moved in the direction of the disc package. After overcoming the release path existing between piston and disc package, the piston abuts the disc package and compresses the disc package in dependence on the oil pressure being applied, whereby the output shaft and the input shaft are connected non-positively to each other. When the piston is relieved of the oil pressure, it is pressed back by the restoring springs of the clutch and the clutch is disengaged in this way.
To ensure the secure separation of the clutch, a certain release path has to be observed whose size depends not only on production tolerances of the discs, but also on the wear of the clutch. As the wear of the discs increases, the release path also becomes longer. With known prior multi-disc clutches, it is disadvantageous that the time slope of the clamping pressure of the piston on the disc package is dependent on the size of the release path to be covered. It follows from this that production tolerances or clutch wear increasing in operation impact on the shift characteristic of the clutch. This can, for example, lead to the clamping pressure increasing in a relatively short time with increased wear, which results in a correspondingly short actuation of the clutch.